Condensed Consolidated Statements Of Equity - USD ($) $ in Thousands		Total	Common Stock [Member]	Capital Surplus [Member]	Accumulated Other Comprehensive Loss [Member]	[1]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2018		$ 1,741,441	$ 601	$ 21,103	$ (87,662)		$ 2,060,440	$ (253,937)	$ 896
Net income		72,410					72,410
Other comprehensive (loss) income		1,146			1,146
Common stock issued under share-based compensation plans		0	1	(1)
Tax withholding for common stock issued under share-based compensation plans		(3,735)		(3,735)
Common stock issued under employee stock purchase plan		1,323		1,323
Common stock dividends		(4,480)					(4,524)
Common stock dividends, accrued dividend shares				44
Distributions to noncontrolling interests		(40)							(40)
Share-based compensation expense		3,557		3,557
Balance at Mar. 31, 2019		1,811,622	602	22,291	(86,516)		2,128,326	(253,937)	856
Balance at Dec. 31, 2019		2,057,780	604	32,274	(89,288)		2,367,481	(253,937)	646
Net income		75,665					75,665
Other comprehensive (loss) income		(2,434)			(2,434)
Cumulative-effect adjustment (2)	[2]	(2,307)					(2,307)
Common stock issued under share-based compensation plans		1	1
Tax withholding for common stock issued under share-based compensation plans		(2,492)		(2,492)
Common stock issued under employee stock purchase plan		1,638		1,638
Common stock dividends		(4,500)					(4,534)
Common stock dividends, accrued dividend shares				34
Repurchase of common stock		(99,048)						(99,048)
Share-based compensation expense		3,291		3,291
Balance at Mar. 31, 2020		$ 2,027,594	$ 605	$ 34,745	$ (91,722)		$ 2,436,305	$ (352,985)	$ 646

[1] Represents cumulative foreign currency translation adjustments and post retirement liability adjustments.

[2] Represents adjustment to retained earnings upon the adoption of Accounting Standards Codification Topic 326.